1. Technical Field
The present invention generally relates to a physical unidirectional communication structure and method and, more particularly, to a communication apparatus and method that generate a separate electrical signal transmission path through which data cannot be transmitted or received so as to solve the reliability problem of transmission that occurs due to the structural limitation of a physical unidirectional data transfer, thus allowing a transmitting side to detect the status of a receiving side.
2. Description of the Related Art
A physical unidirectional data transfer system denotes network security equipment that physically blocks the transmission of data from an external network to an internal network (local network) while enabling the transmission of data from the internal network to the external network, thus fundamentally preventing intrusion made via the external network.
Physical unidirectional data transfer technology includes technology for exploiting an Unshielded Twisted Pair (UTP) cable after cutting the reception (RX) line thereof, technology for cutting and exploiting a serial cable, technology for eliminating the RX line of a photoconverter, etc.
However, such a scheme for cutting a line and physically transmitting unidirectional data has a risk of data loss. In order to compensate for such data loss, there are presented a method of adjusting the size of a buffer and a transfer rate, a method of using a separate control line (using data), etc. However, in a situation in which the status of the receiving side is not known, such a buffer size or transfer rate adjustment method is not a perfect countermeasure. Further, the method of using a separate circuit line has the possibility of the control line itself being misused as an intrusion path.
That is, existing physical unidirectional data transfer technology eliminates the RX line of an internal network connection system in a data transmission section to guarantee physical unidirectionality. By means of this method, malicious data transfer attempted via an external network connection system may be fundamentally blocked, but a problem arises in that the reliability of data is deteriorated.
Korean Patent Application Publication No. 10-2011-0040004 entitled “System and method for transferring data only in one direction” relates to a unidirectional data transfer system and method that transmit data from a network requiring high security to a network requiring low security. This patent discloses technology for physically blocking access from a low-security network to a high-security network while transmitting data from the high-security network to the low-security network. However, the above patent does not present technology in which a separate unidirectional line capable of transferring the status information of a receiving side is used and in which the status of the receiving side is transferred to a transmitting side through the line. That is, the above patent does not mention technology for transferring context, such as a data reception failure or the occurrence of a problem on a receiving side and then guaranteeing the reliability of data transmission in a unidirectional section using a method, such as data retransmission or delayed transmission.